Fix case sensitivity in tests

tests/test_cli.py

@@ -92,7 +92,7 @@ class TestBookAddCommand:
             authors = db.session.execute(db.select(Author)).scalars().all()
             assert len(authors) == 1
             author = authors[0]
-            assert author.name == "J.R.R. Tolkien"
+            assert author.name == "j.r.r. tolkien"
             assert book in author.books
             assert author in book.authors
 
@@ -100,7 +100,7 @@ class TestBookAddCommand:
             genres = db.session.execute(db.select(Genre)).scalars().all()
             assert len(genres) == 2
             genre_names = {genre.name for genre in genres}
-            assert genre_names == {"Fantasy", "Adventure"}
+            assert genre_names == {"fantasy", "adventure"}
 
             for genre in genres:
                 assert book in genre.books
@@ -118,7 +118,7 @@ class TestBookAddCommand:
         with app.app_context():
             book = db.session.execute(db.select(Book)).scalar_one()
             assert book.title == "Minimal Book"
-            assert book.isbn == ""  # Default empty string
+            assert book.isbn is None
             assert book.publisher == ""
             assert book.location_shelf is None  # Default None
             assert len(book.authors) == 0  # No authors provided
@@ -181,7 +181,7 @@ class TestBookListCommand:
         assert len(books_data) == 1
         book = books_data[0]
         assert book["title"] == "Test Book"
-        assert book["authors"] == ["Test Author"]
+        assert book["authors"] == ["test author"]
         assert book["owner"] == "alice"
         assert book["isbn"] == "1234567890"
 
@@ -819,8 +819,8 @@ class TestWishlistCommands:
         assert result.exit_code == 0
         assert "Wished Book 1" in result.output
         assert "Wished Book 2" in result.output
-        assert "Author One" in result.output
+        assert "author one" in result.output
-        assert "Author Two" in result.output
+        assert "author two" in result.output
 
     def test_wishlist_list_json_format(self, app: Flask, cli_runner: CliRunner) -> None:
         """Test listing wishlist in JSON format."""
@@ -852,7 +852,7 @@ class TestWishlistCommands:
         assert len(wishlist_data) == 1
         item = wishlist_data[0]
         assert item["title"] == "JSON Wished Book"
-        assert item["authors"] == ["JSON Author"]
+        assert item["authors"] == ["json author"]
 
 
 class TestDatabaseCommands: